Means for preventing sparking in direct-current machines.



A. FAHRMBACHER.

MEANSFOR PREYENTING SPARKING IN DIRECT CURRENT MACHINES. APPLICATION FILED JAN. 21, 1915.

1,215,787. Patented Feb.13,l917.

ing winding oi the main machine;

both rommutating wind UNITED sTATEs- PATENT OFFICE.

ALOIE) FAHRMBACHER, OF BERLIN-CHARLOTTENBURG, GERMANY, ASSIGNOR TO "1H8 SGHUCKERTWERKE G. M. B. H., 01 SIEMENSSTADT, NEAR BERLIN, MANY, A CORPORATION OF GERMANY.

MEHNS FOR IREVENTING SPARRING IN DIRECT-CURRENT MACHINES. V

Specification. of Letters Yatent.

Patented Feb. 13, 1917.

(iriginal application filed October 22, 1912, Serial No. 727,13i. Divided and this application filed January scribed in the application. Ser. No. 651,794,

and a primary object is to obtain a commutating field which is as favorable as possible with a wide range of speed I/ To this end, I provide the auxiliary Ina-' chine with a second field winding which opposes the main field 'vinding thereof through which fiows the'main current or a i 5311MB.

i1 .tion is diagrammatically represented in "he accompanying drawing, where" in:-

Figure 1 shows one form of my invention in which the auxiliary machine has a selfexciting shunt winding which opposes the main field-Winding thereof;

Fig 2 shows. another form, in which the auxiliary-n'iachine has a counter compounding winding;

Fig. 3' shows a modified form corresponding to that shown in Fig. 2, but in which the main field-winding of the auxiliary machine is connected in parallel with the commutatl ig. l shows another modification in which the main field-winding of the auxiliary machine is connected in shunt to the compensating winding of the main machine;

Fig. 5 shows another modification in which the main fieldqvindmg or the auxiliary machine is connected in shunt across the ymnsating winding and the .g of the main machine.

6 is a diagram showing the variations of commutating fields with the speed.

Serial No. 3,527.

In the above-mentioned application Serial No. 651,794 an arrangement f5! preyenting sparking in direct-current machines s described, in which the comrhutating field 1s influenced by an auxiliary machine which runs s nchronously with the main machine and works on a second commutating Windng connected oppositely to the commutatlng winding proper. Consequently, when the speed increases the commutating field is weakened. A commutating field is obtained which corresponds fairly exactly to the curve I in Fig. 6 of the present application, which is Fig. 1 of the parent application and which indicates the dependence of the commutating field F on the number of revolotions N when the strength of current remalns constant.

Now it has been found by tests that such a commutating field as indicated by the curve I of Fig. 6 does not result into the most favorable commutating conditions, On the contrary, a commutating field curve, as indicated by the curve II in Fig. 6 would correspond to the most favorable commuta' tion, This curve II at first tends to run approximately coincident with curve I; at high speed however, it tends to run appro'ximately parallel with the axis of the abscissas. v

Now in order to obtain as favorable a commutating field curve as possible, I provide the auxiliary machine with a second field winding which opposes the/main field-winding through which the main current or a part of the same passes. 7

Such an arrangement is shown for example in Fig. 1, The main machine is here designated a, while I), denotes the auxiliary machine; 7' is the main field-winding of the .main machine and e the main field-winding of the auxiliary machine. In this arrangement the auxiliary machine is provided with a self-exciting shunt winding n which acts oppositely to the main field winding 6. Consequently the excitation of the auxiliary machine h is at first weakened only little, while when the speed increases it is weakened more. Consequently, in this arrangement the course of the coinmutating field represented by curve II in Fig. (3 is obtained. .The action of theshunt winding corresponds to the difference d of the curves I andII in rangeinent represented in connected in shunt -1n dependence of its speed Fig. 6 which is only small at low speeds, while it is greater at high speeds.

A similar effect is obtained by the ar- Fig. 2-, infwhich the auniliary'machine h is provided with a counter compound winding is which likewise opposes the main field-winding 6. Ac cording" to the invention it is thus immaterial whether the second winding is or of the auxiliary dynamo be fed in series or in shunt by the armature it. It is essential however, that the second fieldwinding n or is shall oppose the main fieldwinding 6. Moreover, the main field-winding c may be fed in series by the main current, as is represented in Figs. 1 and 2.

(in the other hand, as shown by way of example in Fig. 3, which otherwise corresponds with the arrangement shown in Fig. 2, the field-winding 0 may be connected in parallel with the comnrutating winding 10 of the main machine, or, as in Fig. 5, be to the. compensation winding 0 or as in Fig. 6, be connected in shunt across the compensation windingc and the commutating winding 10 connected in series. i

claim l. in a direct-current dynamo electric machine oi the character described, the combination oi: a main dynamo havin a cominutating winding; an additional winding for counteracting" said commutating wind int an auxiliary dynamo coupled with said main dynamo for supplying current to said additional winding; and means for varying the voltage oi said auxiliary dynamo in a predetermined manner as a non-linear function of the speed. i

2. ln a direct-current dynamo electric machine of the character described, the combination of a main dynamo having a corn mutating winding; additi nal winding for counteracting said coinmni ting winding; an auxiliary dynamo coupled with said main dynamo for supplying" current to said additional winding; and means changing'the voltage of said auxiliary dynamo more rapidly at relatively low speed and less rapidly at relatively high speed.

3. in a direct current dynamo electric machine oi the character described, the com- 4 bination of a main dynamo having a commutating winding; an additional winding for counteracting said conimutating winding'; an auxiliary dynamo coupled with said main dynamo for supplying current to said additional Winding; and means for varying the voltage of said auxiliary dynamo so as" to more slowly increase at relatitely high speed and so as to more rapidly increase at relatively low speed.

mutating winding; an

' pendence on the 4%. In direct current dynamo electric machine of the character described, the com bination of a main dynamo having a coin mutating winding; an'auxiliary dynamo geared to said. main dynamo; an additional winding mounted to cotiperate with said commntating winding; connections between said auxiliary'dynamo and said additional winding for counteracting'the effect of said commutating winding with increasing speed ot"said main and said auxiliary dynamo; a main field-winding for saidauxiliary dynamo connected to be energized in do pendence on the current generated by the armature of said main dynamo; and a further winding .on said auxiliary dynamo which is excited from the armature thereof and mounted to oppose the action of the main field-winding thereof.

,5. in a direct current dynamo electric machine of the character described, the combination of a main dynamo having a comauxiliary dynamo geared to said main dynamo; an additional winding mounted to coiiperate with said commutating winding; connections between said auailiary dynamo and said additional winding for counteracting the etlect of? said commutating winding with increasing speed of said main and said auxiliary dynamo;

a main field-winding for said auxiliary dy-' narno connected to he energized in dccurrent armature of said main dynamo; and a shunt winding on said auxiliary dynamo connected to oppose the action of'the main fieldwinding thereof. v

6. in a direct-current dynamo electric machine of the character described, the comination ofc main dynamo having a coinmutating. winding; an auxiliary dynamo geared to said main dynamo; an additional winding on said main dynamo 1n the axis of said commutating winding; connections between said auxiliary dynamo and said additional winding for opposing the action of said conimutating winding with increasing speed of said main and auxiliary dynamo; a main field-winding on said auxiliary dynamo which is connected in series to the armature ot' said-main dynamo; and a selfeirciting shunt winding on said auxiliary dynamo connected to oppose the action of the main field-Winding thereof.

In testimony whereof I have hereunto set my signatnre in the presence of two subscribing witnesses.

ators FAHRMBAOHER.

Witnesses N. llonnnn, Vio'ron Gnoonnnniionn.

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